Re: [Gpredict-discussion] Forecasting RAAN

[Alexandru C. <oz...@gm...>]

Hi guys,

It is not possible to predict RAAN using gpredict because RAAN is an
input parameter to the SGP4/SDP4 algorithms that are used by gpredict.

Also, please be aware of the general limitations and scope of gpredict
and the SGP/SDP algorithms. These are numerical approximations useful
for short term (few weeks) predictions of medium accuracy and that's
it. Even if the algorithms could be stretched beyond that, I never
really performed any validation of the implementation found in
gpredict.

Alex


On Wed, Oct 23, 2013 at 4:18 AM, Ryan Caron <rc...@ig...> wrote:
> Depends what you mean by "forecast". The Orbit Info from the Satellite
> Info dialog lists the current RAAN.
>
> If you want how RAAN changes over long time scales it doesn't appear
> Gpredict can do that. I tried using the Time Controller to go forward 6
> months to see if the ISS' RAAN changed. It didn't (but just updating
> just a stale TLE took me from 330 degrees to 196).
>
> Based on the current information on ISS' orbit, and
> http://en.wikipedia.org/wiki/Nodal_precession
>
> I get ISS' orbit precession as -1.238 degrees/day (not accounting for
> things like maneuvers of course).
>
> Hope this helps!
>
> --
> 73,
> Ryan
> NX1U
>
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